Ram tensioning device

ABSTRACT

A ram tensioning device comprising a hydraulic-pneumatic cylinder with a free piston disposed within the cylinder, a piston rod extending from one end of the cylinder the piston rod being acted upon by pneumatic fluid to provide shock absorbing tensioning for a hoist cable and being acted upon via the free piston by a hydraulic fluid to provide accurate positioning of the piston rod to assist in handling heavy variable loads which are ideally subjected to a constant tensional force in one mode of operation and firmly positioned in another mode of operation.

ited States Patent [191 Schimmeyer et a1.

[ Mar. 18, 1975' RAM TENSIONING DEVICE [75] Inventors: Werner K. Schimmeyer, Los Altos; Norman J. Wood, San Jose; Joseph V. McCargar, Los Altos, all of Calif.

[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

[22] Filed: Apr. 4, 1973 [21] Appl. No.: 347,980

[52] US. Cl 212/3, 92/8, 92/129, 254/172, 254/189 [51 Int. Cl. 1366c 23/52 1 [58] Field of Search 212/3; 254/189, 172; 92/8, 92/129, 134, 75, 62, 63; 91/165, 390; 188/317, 314; 244/110 G, 110 C, 63;

[56] References Cited UNITED STATES PATENTS 2,588,037 3/1952 Orton 254/172 2,897,907 8/1959 Blount et a1. 254/189 3,265,218 8/1966 Stefanutti 254/189 3,311,351 3/1967 Blakely 254/189 3,415,159 12/1968 Hornlein et a1 92/134 3,531,065 9/1970 Brown 92/8 3,638,423 2/1972 Van Heijst 92/134 3,719,041 3/1973 Barnard et al. 92/62 Primary Examiner-Evon C. Blunk Assistant ExaminerJeffrey V. Nase Attorney, Agent, or FirmF. J. Baehr, Jr.

[57] ABSTRACT A ram tensioning device comprising a hydraulicpneumatic cylinder with a free piston disposed within the cylinder, 3 piston rod extending from one end of the cylinder the piston rod being acted upon by pneumatic fluid to provide shock absorbing tensioning for a hoist cable and being acted upon via the free piston by a hydraulic fluid to provide accurate positioning of the piston rod to assist in handling heavy variable loads which are ideally subjected to a constant tensional force in one mode of operation and firmly positioned in another mode of operation.

6 Claims, 3 Drawing Figures RAM TENSIONING DEVICE BACKGROUND OF THE INVENTION This invention relates to aerospace and marine applications wherein large amplitude vibrations occur and accurate positioning is required when lifting heavy loads with a deck crane. This invention is applicable to a deck crane of a ship, wherein the crane is required to lift heavy loads from the water and the apparent weight of the object varies as the object emerges from the water due to the loss of buoyancy. It is also applicable where some type of tensioning device is necessary to take up or play out slack in the hoist line as the ship and hoist heave as a result of waves or swells.

SUMMARY OF THE INVENTION In general, a ram tensioning device, when made in accordance with this invention, comprises a tubular housing, a first movable abutment slidably disposed within the housing, a second movable abutment slidably disposed within the housing and a rod extending from one of the abutments. One end of the housing is closed forming a chamber between the closed end of the housing and the first movable abutment. A second chamber is formed between the first and second movable abutment. The rod tensioning device also comprises means for supplying pressurized gaseous fluid to one of said chambers and means for supplying pressurized hydraulic fluid to the other of said chambers at a pressure greater than the gaseous fluid being supplied to the other chamber.

BRIEF DESCRIPTION OF THE DRAWINGS The objects and advantages of this invention will become more apparent from reading the following detailed description in connection with the accompanying drawings in which corresponding reference characters indicate corresponding portions throughout the drawings, and in which:

FIG. 1 is a schematic diagram of a deck hoist mounted on a ship and the hoist has a ram tensioning device, made in accordance with this invention, disposed thereon;

FIG. 2 is a sectional view of the ram tensioning device; and

FIG. 3 is a flow diagram showing the control of the liquid and gaseous pressurized fluids being supplied to the ram tensioning device.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings in detail, FIG. 1 shows a portion of a ship 1 having a deck crane 3 pivotally mounted thereon. The deck crane 3 comprises a base 5, a hoist drum 7 rotatably disposed in the base 5, a motor or other driving means (not shown) connected to the hoist drum 7, and a boom 9 pivotally connected to the base by a pin 11. A boom positioning drum 13 driven by a boom positioning motor or means (not shown) is disposed on the upper portion of the base 5 and a positioning cable or line 15, preferably a wire rope, wraps around the positioning drum l3 and is fastened to the upper or free end of the boom 9 to raise and lower the boom as the positioning cable is wound and unwound from the positioning drum 13. A twogroove head sheave 17 is rotatably disposed on the free end of the boom 9 and a ram tensioning device 19 is fastened to the boom in such a manner that one end is fixed thereto and the other end is free to move rectilinearly away from the head sheave 17. A moving sheave 21 is rotatably disposed on the free or moving end of the ram tensioning device 19.

A hoist line or cable 23, preferably a wire rope, wraps around the hoist drum 7, extends upwardly and wraps over a portion of one groove in the head sheave 17, runs downwardly along the side of the boom 9, makes a turn over the moving sheave 21, extends upwardly alongside the boom 9, wraps over a portion of the second groove in the head sheave l7, and extends downwardly to a weight or load 25 to be lifted by the crane 3.

As shown in FIG. 2, the ram tensioning device 19 comprises a tubular housing or cylinder 31, a first movable abutment or piston 33 slidably disposed within the tubular housing 31 and a second movable abutment, a floating or free piston 35, slidably disposed within the tubular housing 31. A piston rod 37 fastened to and extends axially from the first piston 33. The piston rod 37 has a cross sectional areasmaller than the first piston 33 forming an annular chamber 39 between the piston rod 37 and the tubular housing 31.

Sealing means comprising an O-ring 41 and a circumferential groove 43 are disposed adjacent one end of the tubular housing to form a sliding seal between the piston rod 37 and the tubular housing 31.

The other end of the housing is closed forming a chamber 45 between the closed end of the housing 31 and the free piston 35.

The free piston 35 and the piston 33 are so disposed within the housing 31 to form a chamber 47 therebetween. The piston 33 has a plurality of openings 49 disposed therein forming means for allowing a controlled rate of fluid flow between the annular chamber 39 and the chamber 47.

A hydraulic fluid inlet port 51 is disposed in the closed end of the tubular housing 31 forming means for supplying pressurized hydraulic fluid to the chamber 45 disposed between the housing 31 and the piston 35.

A gas inlet port 53'is disposed adjacent the open end of the tubular housing 31 forming means for supplying pressurized gaseous fluid to the annular chamber 39. The pressure which can be delivered by the hydraulic fluid is substantially higher than the pressure which can be developed by the gaseous or pneumatic fluid, allowing the hydraulic fluid to override the pneumatic fluid.

FIG. 3 shows a flow diagram of the control of the fluids utilized to operate the ram tensioning device 19, in which a reservoir 61 containing hydraulic fluid is fluidly connected to the hydraulic supply port 51 via a conduit 63. A hydraulic pump 65 is disposed in the conduit 63 and is adapted to take its suction from the reservoir 61 and to discharge into the conduit 63, to supply pressurized hydraulic fluid to the chamber 45. A hydraulic control valve 67 is disposed in the conduit 63 between the pump 65 and the chamber 45 to control the flow of hydraulic fluid being supplied to the chamber 45. A pressure relief valve 69 is disposed in fluid communication with the conduit 63 between the pump 65 and the control valve 67. The pressure relief valve 69 is also in fluid communication with the reservoir 61. The pressure relief valve 69 limits the pressure in the conduit 63 to a predetermined level by relieving the pressure into the reservoir when it exceeds the predetermined level.

A cylinder ofpressurized gas 71 is fluidly connected to the gas inlet port 53 via a conduit 73. A pressure regulator 75 is disposed in the conduit 73 adjacent the cylinder of pressurized gas. Also disposed in the conduit 73, immediately downstream of the pressure regulator 75, is a shut-off valve 77 and downstream of the shutoff valve is a cross 78. One branch 79 of the cross 78 is in fluid communication with a vent valve 81, while the other branch 83 of the cross 78 is in fluid communication with an accumulator or expansion chamber 85. An isolation valve 87 is disposed in the branch 83 between the cross 78 and the expansion chamber 85.

The operation of the ram tensioning device 19 is as follows:

The pressure regulating valve 75 is adjusted to some predetermined pressure depending on the load or weight to be lifted. The shut-off valve 77 and isolation valve 87 are open and the vent valve 81 is closed allowing the pressurized gaseous fluid from the cylinder 71 to fill the expansion chamber 85 and the chambers 39 and 47 in the ram tensioning device. The pressurized gaseous fluid in the chambers 39 and 47 react on the piston 34 to extend the piston rod a predetermined amount depending on the weight or load 25 being lifted as the drum 7 takes up the cable 23 to lift the load 25. As the load 25 isbeing lifted through the water, the gaseous fluid absorbs shock and moves the piston rod 37 in and out to take up slack or pay out line as the ship pitches or rolls in order to generally keep a constant tension on the hoist line 23. The expansion chamber 85 can be put in and taken out of service to drastically change the volume of the gaseous fluid in the system, thus changing the response of the tensioning system. Changing the set pressure by adjusting the pressure regulating valve 75 will also change the response of the tensioning system.

As the weight or load is raised through the air-water interface additional lifting capacity is required due to the loss of buoyancy. At this stage of the operation the hydraulic control valve 67 is opened allowing pressurized hydraulic fluid to enter the chamber 45 driving the free piston 35 toward the piston 33 to further extend the piston rod 37 and rapidly lift the weight 25. During this mode of operation when the hydraulic fluid is being utilized to extend the piston rod 37 to lift load it is desirable to lock the hoist drum 7 to prevent its rotation so that it will not pay out hoist line 23 as the hydraulic fluid exerts a large force on the hoist line through the piston rod and movable sheave 21.

The ram tensioning device 19, hereinbefore described, advantageously provides tensioning of the hoist line 23 taking up slack and paying out hoist line so that there is generally a constant force being applied to lift the weight 25 even though the ship 1 and deck crane 3 are subjected to a heaving motion due to swells or waves. The spring constant or response of the pneumatic portion of the tensioning system can be easily changed to accommodate various loads by changing either the set pneumatic pressure or by varying the volume as hereinbefore described.

The hydraulic portion of the tensioning device produces a high lifting capacity with precision and speed not available with comparably priced motor driven hoists. Such a ram tensioning device also advantageously allows the utilization of a hoist drive system, wherein the hoist drive can be sized for raising and lowering the weight or load in the water, where the speed is low and the load is reduced by the buoyancy of the water, and a hydraulic system for lifting heavy loads a short distance at a high rate of speed resulting in considerable savings in hoist drive costs.

What is claimed is:

1. A boom in combination with a drum and cable for hoisting a load and a ram tensioning device attached to said boom and cooperatively associated with said cable, said ram tensioning device comprising a tubular housing, a first movable abutment slidably disposed within said housing, a second movable abutment slidably disposed within said housing, a rod extending from one of said abutments and extending beyond said housing, said housing having a closed end, a first chamber disposed between said closed end and said first movable abutment, a second chamber disposed between said first and second abutments, means for supplying pressurized gaseous fluid to one of said chambers, and means for supplying hydraulic fluid to the other of said chambers at a pressure greater than the gaseous fluid, whereby during operation the gaseous fluid maintains a generally constant tension on the cable and the hydraulic fluid is utilized to rapidly lift the load.

2. The combination set forth in claim 1, wherein the means for supplying gaseous fluid is disposed adjacent the end of the housing from which the rod extends.

3. The combination set forth in claim 1, wherein the means for supplying pressurized hydraulic fluid is disposed adjacent the closed end of the housing.

4. The combination set forth in claim 1, wherein the I housing is cylindrically shaped and the rod has a round cross section so as to form a third chamber between the rod and the housing, there is an opening in the second movable abutment and the means for supplying pressurized gaseous fluid is in fluid communication with said third chamber.

5. A boom in combination with a drum and cable for hoisting a load and a ram tensioning device attached to said boom and cooperatively associated with said cable, said ram tensioning device comprising a tubular housing, a first movable abutment slidably disposed within said housing, a second movable abutment slidably disposed within said housing, a rod extending from the first movable abutment, said first and second movable abutments being so disposed to form a first chamber therebetween, one end of said housing being closed, said second movable abutment cooperating with said closed end of said housing to form a second chamber, means for supplying pressurized gaseous fluid to one of said chambers and means for supplying pressurized hydraulic fluid to the other of said chambers, at a pressure greater than the gaseous fluid, whereby during operation the gaseous fluid maintains a generally constant tension on the cable and the hydraulic fluid is utilized to rapidly lift the load.

6. The combination as set forth in claim 5, wherein the gaseous fluid is supplied to the first chamber and the hydraulic fluid is supplied to the second chamber. 

1. A boom in combination with a drum and cable for hoisting a load and a ram tensioning device attached to said boom and cooperatively associated with said cable, said ram tensioning device comprising a tubular housing, a first movable abutment slidably disposed within said housing, a second movable abutment slidably disposed within said housing, a rod extending from one of said abutments and extending beyond said hOusing, said housing having a closed end, a first chamber disposed between said closed end and said first movable abutment, a second chamber disposed between said first and second abutments, means for supplying pressurized gaseous fluid to one of said chambers, and means for supplying hydraulic fluid to the other of said chambers at a pressure greater than the gaseous fluid, whereby during operation the gaseous fluid maintains a generally constant tension on the cable and the hydraulic fluid is utilized to rapidly lift the load.
 2. The combination set forth in claim 1, wherein the means for supplying gaseous fluid is disposed adjacent the end of the housing from which the rod extends.
 3. The combination set forth in claim 1, wherein the means for supplying pressurized hydraulic fluid is disposed adjacent the closed end of the housing.
 4. The combination set forth in claim 1, wherein the housing is cylindrically shaped and the rod has a round cross section so as to form a third chamber between the rod and the housing, there is an opening in the second movable abutment and the means for supplying pressurized gaseous fluid is in fluid communication with said third chamber.
 5. A boom in combination with a drum and cable for hoisting a load and a ram tensioning device attached to said boom and cooperatively associated with said cable, said ram tensioning device comprising a tubular housing, a first movable abutment slidably disposed within said housing, a second movable abutment slidably disposed within said housing, a rod extending from the first movable abutment, said first and second movable abutments being so disposed to form a first chamber therebetween, one end of said housing being closed, said second movable abutment cooperating with said closed end of said housing to form a second chamber, means for supplying pressurized gaseous fluid to one of said chambers and means for supplying pressurized hydraulic fluid to the other of said chambers, at a pressure greater than the gaseous fluid, whereby during operation the gaseous fluid maintains a generally constant tension on the cable and the hydraulic fluid is utilized to rapidly lift the load.
 6. The combination as set forth in claim 5, wherein the gaseous fluid is supplied to the first chamber and the hydraulic fluid is supplied to the second chamber. 